This application claims the priority of German Patent Document 101 54 150.3, filed on Nov. 3, 2001, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a fuel tank comprising a tank venting system and a sucking jet pump which feeds fuel into a sucking-jet-pump feedline which fills a storage pot arranged in the tank, the sucking jet pump having a driving nozzle.
In fuel tanks, in particular in motor vehicles, fuel constantly evaporates as a function of vapor pressure, ambient pressure, temperature and movement. In order to avoid an excessive pressure load on the fuel tank, fuel tanks have a ventilation and venting system. In order to prevent hydrocarbon emissions during the venting, a regenerating activated carbon filter which adsorbs hydrocarbons can be provided in the venting system. For regeneration purposes, the activated carbon filter has air flowing through it, and the fuel vapor/air mixture which arises is supplied to the internal combustion engine for combustion. The activated carbon filter is severely loaded by the fuel vapor. In order to relieve the activated carbon filter of load, recondensation lines are known. The latter conduct the fuel vapors which arise during refuelling back into the filler-neck head, so that they become liquid in the refuelling flow and flow together with the latter into the tank. However, this recondensation device is only active during the refuelling process.
An aspect of certain preferred embodiments of the invention is based on providing a fuel tank of the above type which enables the fuel vapors which arise to be continuously condensed.
This aspect is achieved by a fuel tank in which a line leads from a region of the tank roof into a negative pressure region of the sucking jet pump.
The line leading from the region of the tank roof into a negative pressure region of the sucking jet pump continuously sucks fuel vapor from the region of the tank roof into the fuel flow flowing through the sucking jet pump. The fuel vapor is liquefied in the process. The load on the activated carbon filter is reduced by the continuous sucking of the fuel vapors into the sucking jet pump, since the exposure of the filter to fuel vapor is minimized. The required regeneration of the activated carbon filter is thereby reduced. This is advantageous particularly in the case of directly injected spark-ignition engines, since with the latter the required regenerating rates for the activated carbon filter can no longer readily be made available.
The lower load on the activated carbon filter increases its service life. Since the risk of “bleeding emissions” is reduced by the lower loading of the activated carbon filter, fuel vapor emissions can be minimized. In addition to the active regeneration of the activated carbon filter via the regenerating system, a gradual, passive regeneration of the activated carbon filter takes place, since by way of the condensation of the hydrocarbon molecules in the tank a negative pressure is produced therein causing air to be sucked through the activated carbon filter into the tank, the air thereby regenerating the activated carbon.
Provision is made for the line to be designed as a section of hose. The production of the line is thus particularly cost-effective and simple. A mixing tube is advantageously arranged downstream of the driving nozzle. The line expediently opens into a negative pressure region in the mixing tube. Good fixing of the line is thus possible. Furthermore, a good sucking power is produced and the function of the sucking jet pump is only slightly affected. Provision is made for the line to open into the mixing tube approximately parallel to the direction of flow therein. Particularly favorable flow ratios are therefore produced in the mixing tube. However, it may be expedient for the direction of flow of a fluid emerging from the line into the mixing tube to be inclined by an angle of less than 90° with respect to the direction of flow in the mixing tube.